Critical current fluctuations in Josephson junctions

The novel opportunities offered by nanotechnologies and materials science have enlarged the physical conditions of occurrence of the Josephson effect. Semiconducting, ferromagnetic, topological-insulator, and graphene barriers lead to unconventional and anomalous aspects of the Josephson coupling, which might be useful to respond to some issues on key problems of solid-state physics. However, the complexity of the layout and the competing physical processes occurring in the junctions pose novel questions on the interpretation of their phenomenology. Measurements of critical current fluctuations have turned to be imaging tools of different dissipation processes, whose origin may depend on the type of the barrier, the nature of the interface, the geometry and dimensionality of the device. In this chapter, we classify some significant behaviors of unconventional junctions in terms of the temperature properties of the critical current fluctuations, thus providing accurate arguments to distinguish and understand physical processes occurring in quite different dynamical regimes. These notions are universal and apply to all kinds of junctions.